The present invention generally relates to a method of determining the sensitivity of the fatigue life of a structural component with respect to particular design parameters.
Fatigue failure is the most common mode of failure for a structural component. Generally, there are three accepted methods of performing fatigue analysis. These methods are stress-life, strain-life and linear elastic fracture mechanics. Among these three, the stress-life (Sxe2x80x94N) method is most widely used, particularly in the automotive industry. There has not been a widespread use of the strain-life and linear elastic fracture mechanics methods in the industry, and therefore, there is limited experience and confidence in these methods.
When performing an Sxe2x80x94N type fatigue analysis, there are two different approaches. The first approach is a time domain application and the second approach is a frequency domain application. The basic idea in a time domain approach is to apply the rain flow counting process to the fatigue stress history of a structural component to determine the accumulative damage of the structural component. For the frequency domain approach, there is a narrow band method and a wide band method. Both the narrow band and wide band methods of the frequency domain approach simulate the rain flow counting process just as with the time domain approach. However, the frequency domain approach is more efficient, in terms of computer time and resources, due to the simplicity of application and quick turn around time of both the dynamic stress simulation and the fatigue life analysis.
A unique feature of the frequency domain approach is that an analytical model of the structural component can be used to predict the fatigue life of the structural component in terms of specific design parameters of the structural component. This feature is what makes the frequency domain approach widely used in the automotive industry. Unfortunately, all the existing frequency domain approaches focus only on identifying the points of higher stress and predicting the ultimate fatigue life of the component. Therefore, there is a need in the industry for a method of identifying the points of a structural component which are most susceptible to fatigue damage and predicting the ultimate fatigue life of the structural component as well as providing insight on how specific design parameters of the structural component can be changed to increase the fatigue life of the structural component. The relationship between the fatigue life and the specific design parameters of the structural component are described and quantified by the sensitivity of the fatigue life of the structural component with respect to the particular design parameters.